title: Seasonality of diarrheagenic Escherichia coli pathotypes in the US students acquiring diarrhea in Mexico.
abstract: BACKGROUND
  Up to 60% of the US visitors to Mexico develop travelers' diarrhea (TD). In Mexico, rates of diarrhea have been associated with the rainy season and increase in ambient temperature. However, the seasonality of the various diarrheagenic Escherichia coli pathotypes in travelers has not been well described.
  
  
  OBJECTIVE
  A study was undertaken to determine if ambient temperature and rainfall have an impact on the acquisition of TD due to different diarrheagenic E coli pathotypes in Mexico.
  
  
  METHODS
  We conducted a cohort study of the US adult students traveling to Cuernavaca, Mexico, who were followed during their stay and provided a stool sample with the onset of TD. The presence of E coli was analyzed by a direct fecal multiplex polymerase chain reaction for common E coli pathotypes including enterotoxigenic, enteropathogenic, enteroinvasive, shiga toxin-producing, and enteroaggregative E coli (ETEC, EPEC, EIEC, STEC, and EAEC respectively). The presence of pathotypes was correlated with daily rainfall, average, maximum, and minimum temperatures.
  
  
  RESULTS
  A total of 515 adults were enrolled from January 2006 to February 2007. The weekly attack rate of TD for newly arrived travelers was lower in the winter months (range 6.8%-16.3%) than in summer months (range 11.5%-25%; p = 0.05). The rate of ETEC infection increased by 7% for each degree centigrade increase in weekly ambient temperature (p = 0.003). In contrast, EPEC and EAEC were identified in similar proportions during the winter and summer seasons.
  
  
  CONCLUSIONS
  Temperature variations in central Mexico influenced the rate of ETEC but not EAEC-associated diarrhea in the US visitors. This epidemiological finding could influence seasonal recommendations for the use of ETEC vaccines in Mexico.
authors.affiliation: Medical School, The University of Texas at Houston, Houston, TX 77030, USA.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Paredes-Paredes
authors.forename: Pablo C
authors.initials: PC
authors.lastname: Okhuysen
authors.forename: Jose
authors.initials: J
authors.lastname: Flores
authors.forename: Jamal A
authors.initials: JA
authors.lastname: Mohamed
authors.forename: Ranjit S
authors.initials: RS
authors.lastname: Padda
authors.forename: Alexei
authors.initials: A
authors.lastname: Gonzalez-Estrada
authors.forename: Clinton A
authors.initials: CA
authors.lastname: Haley
authors.forename: Lily G
authors.initials: LG
authors.lastname: Carlin
authors.forename: Parvathy
authors.initials: P
authors.lastname: Nair
authors.forename: Herbert L
authors.initials: HL
authors.lastname: DuPont
mesh_terms: D000328:Adult; D003967:Diarrhea / Q000453:epidemiology / Q000382:microbiology; D054308:Enteropathogenic Escherichia coli / Q000302:isolation & purification; D054307:Enterotoxigenic Escherichia coli / Q000302:isolation & purification; D004926:Escherichia coli / Q000145:classification / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology*; D005243:Feces / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D008800:Mexico; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012621:Seasons; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification; D013334:Students / Q000706:statistics & numerical data*; D014195:Travel; D014481:United States / Q000453:epidemiology; D055815:Young Adult